JOHANNESBURG, Oct. 11 -- Zimbabwean President Robert Mugabe has asserted claim to key disputed ministries, outraging the opposition and imperiling a fragile power-sharing agreement signed three weeks ago.

The state-owned Herald newspaper published a list Saturday that handed the ruling Zimbabwe African National Union-Patriotic Front, or ZANU-PF, the powerful ministries of defense, justice, foreign affairs and home affairs, which controls Zimbabwe's police. Those cabinet posts would essentially secure Mugabe's 28-year grip on power and make the recent deal meaningless.

The Movement for Democratic Change (MDC), the main opposition party, denounced the list as a "midnight ambush" by ZANU-PF and said no agreement on ministries had been reached. The opposition released a list depicting its own "general understanding" of the state of negotiations and showing justice, home affairs and foreign affairs under MDC control.

"It is a giant act of madness which puts the whole deal in jeopardy," MDC spokesman Nelson Chamisa said in a statement.

The ruling party, the MDC and a splinter opposition party have been squabbling for weeks over 31 cabinet slots. On Friday, the parties agreed to summon former South African president Thabo Mbeki, who brokered the power-sharing deal, to help break the deadlock, news services reported.

"ZANU-PF cannot nocturnally allocate ministries barely hours after the three principals agreed to disagree by referring the matter to the mediator after a logjam over all key ministries," Chamisa said.

Mbeki, who was forced to resign last month but remains the official mediator in Zimbabwe, is scheduled to arrive in Harare, the capital, on Monday. But analysts say his diplomatic powers have been diminished.

The Herald said official appointments would be made upon Mbeki's arrival. But the paper said Mbeki's sole task would be to help allocate the finance ministry, which it said "Comrade Mugabe provisionally assigned to ZANU-PF."

MDC leader Morgan Tsvangirai beat Mugabe in the presidential election in March but failed to get the clear majority necessary to avoid a second round of voting. Mugabe then unleashed his security forces in a bloody crackdown on opposition supporters, prompting Tsvangirai to pull out of the June runoff. Mugabe won that vote, which was uncontested and internationally condemned.

The power-sharing deal, signed Sept. 15, made Tsvangirai prime minister and gave the opposition parties 16 cabinet posts.

The agreement was seen as the potential trigger for an influx of aid dollars to Zimbabwe, which has become economically devastated under Mugabe's disastrous policies and increasingly repressive hand. But donors have been waiting to see whether a true unity government was formed.

The United Nations this week appealed for $140 million in aid to help stem severe food shortages in Zimbabwe, where inflation has reached 231 million percent, according to recent government figures.

A Washington Post special correspondent in Harare, Zimbabwe, contributed to this report.